The invention relates generally to the treatment of water by reverse osmosis units, and particularly to those units that require degasification to remove carbon dioxide.
Reverse osmosis membranes are frequently used to treat water to remove certain impurities. The elements making up a reverse osmosis membrane require that water fed to the membrane have a pH below 8.5, otherwise they rapidly lose their capacity to function. In order to achieve the desired pH, water fed to the membrane is often treated by an acid to lower the pH prior to feeding the water to the unit. The combination of acid and water, however, may lead to the generation of carbon dioxide in the water. Since reverse osmosis membranes are permeable to carbon dioxide, the carbon dioxide will remain in the water passed through the unit.
The carbon dioxide, which is undesirable, may be removed by sending the carbon dioxide-loaded water through a degasifier, but this ordinarily requires the expenditure of energy to operate the degasifier. The degasifier operates by passing the water through a tank where the carbon dioxide in the water rises to the top of the tank where a space is maintained. The carbon dioxide is removed from this space.
In U.S. Pat. No. 3,917,526 (Jennings) the stream from a membrane is used to affect the eduction removal of foam from the to of a flotation stage in a process for removing suspended solids, fats, oily wastes, etc. from a liquid stream. The liquid stream passes through the flotation system before entering the reverse osmosis membrane system in the arrangement shown in that patent.
It is an object of the invention to provide for a reverse osmosis/degasifier in which less energy is required for operation.